Two Python Packages Need Updating After a Brotli Decoder Flaw Rated Critical

The GitHub Advisory Database published an advisory on Oct. 22, 2026, extending CVE-2026-111497 to the two Brotli packages on the Python index PyPI, brotli and brotlicffi. A crafted compressed stream can make the Brotli decoder write past the end of an internal buffer, and for both packages, the remedy is a version upgrade.

Few Python projects install Brotli on purpose. It is the compression Google built to shrink web pages and API responses in transit, and the packages arrive underneath something else. urllib3, the HTTP library that the requests package is built on, lists brotli and brotlicffi as its optional Brotli dependencies for reading responses compressed with it. A project can be in scope without anyone having chosen the library.

The advisory gives the affected range for brotli as 1.0.3 up to but not including 1.2.1, patched in 1.2.1, and for brotlicffi as 1.0.3 up to but not including 1.2.1.0, patched in 1.2.1.0. The two patched version strings are not the same; brotlicffi carries the extra component. The advisory also says the underlying C library is affected from 1.0.3 through 1.2.0 on all platforms, and for any Brotli library or binary in that range, it names three fixed releases: 1.0.10, 1.1.1 or 1.2.1.

GitHub marks the advisory as Critical and gives it a CVSS version 4 base score of 9.2, a rating assigned by the scorer rather than a measure of observed attacks. The page records the National Vulnerability Database's own entry for the identifier the same day.

Node.js bundles the same decoder code and patched it in its security releases of Oct. 21, 2026, in versions 22.23.4, 24.22.1 and 26.12.1. The Node.js project rated the issue high rather than critical. The GitHub advisory's title gives the flaw a name, "Node2Shell."

Node.js credits the report to Khai Tran and Sylvie Mayer of OpenAI Codex Security.